title: Characterization and localization of mitochondrial DNA-encoded tRNAs and nuclear DNA-encoded tRNAs in the sea anemone Metridium senile.
abstract: The mitochondrial (mt) genome of the sea anemone Metridium senile contains genes for only two transfer RNAs (tRNAs), tRNAf-Met and tRNATrp. Experiments were conducted to seek evidence for the occurrence of functional tRNAs corresponding to these genes and for the participation of nuclear DNA-encoded tRNAs in mt-protein synthesis. RNA sequences corresponding to the two mt-tRNA genes were located in mitochondria and it was shown that 3'-CC (and possibly A, but no other nucleotide) is added post-transcriptionally to the 3' end of at least 50 % of mt-tRNAf-Met molecules and to a small fraction of the mt-tRNATrp molecules. Using specific oligonucleotide primers based on expected nuclear DNA-encoded tRNAs in a series of RACE experiments, we located the nuclear genes for tRNAGln, tRNAIle, tRNAi-Met, tRNAVal and tRNAThr. Data from Northern blot analyses indicated that mtDNA-encoded tRNAf-Met is limited to mitochondria but that nuclear DNA-encoded tRNAVal and tRNAi-Met are present in the cytoplasm and in mitochondria. These data provide direct evidence that in M. senile, mature, functional tRNAs are transcribed from the mtDNA-encoded tRNAf-Met and tRNATrp genes, and are consistent with the interpretation that both nuclear DNA-encoded tRNAVal and tRNAi-Met are utilized in mitochondrial and cytosolic protein synthesis.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84121, USA. tim.beagley@slcc.edu
authors.forename: C Timothy
authors.initials: CT
authors.lastname: Beagley
authors.forename: David R
authors.initials: DR
authors.lastname: Wolstenholme
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000235:genetics; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D008928:Mitochondria / Q000235:genetics* / Q000378:metabolism; D009690:Nucleic Acid Conformation; D012343:RNA, Transfer / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D012615:Sea Anemones / Q000235:genetics
chemical_list: D004272:DNA, Mitochondrial; D004247:DNA; D012343:RNA, Transfer